U.S. scientists test early warning system for earthquakes

William Atkins
Thursday, 10 July 2008 19:36

Science - Climate

The researchers were able to predict one small (naturally produced) tremor by two hours and a second one by ten hours.

They stated in the abstract to their paper, “Here we show that stress changes are indeed measurable using this technique. Over a two-month period, we observed an excellent anti-correlation between changes in the time required for a shear wave to travel through the rock along a fixed pathway (a few microseconds) and variations in barometric pressure. We also observed two large excursions in the travel-time data that are coincident with two earthquakes that are among those predicted to produce the largest coseismic stress changes at SAFOD. The two excursions started approximately 10 and 2 hours before the events, respectively, suggesting that they may be related to pre-rupture stress induced changes in crack properties, as observed in early laboratory studies.”

Silver explains, "What we're looking for are changes in the velocity that would correspond to changes in stress, and it has been hypothesised that such stress changes would precede seismic events and could be used as precursors. For a long time, people have been trying to do this. I think right now the technology has gotten better so we can measure this change more accurately." [United Press International: “Pre-quake seismic wave changes discovered”]

Silver stated, "If you had 10 hours' warning, from a practical point of view, you could evacuate populations, you could certainly get people out of buildings, you could get the fire department ready. Hurricane (warnings) give you an idea of what could be done." [United Press International]

Although scientists are unable to routinely predict earthquakes, this new advancement provides the technological ability to someday forecast their occurrence similarly to hurricanes, as Silver suggests.

The article, which is based on the research for this early warning sysem, is entitled “Preseismic velocity changes observed from active source monitoring at the Parkfield SAFOD drill site.” It is found in the July 10, 2008 issue of the journal Nature (Nature 454, 204-208 (10 July 2008).

The researchers are now testing the system in China and Japan to see if it is equally able to sense a “preseismic signal” at other locations.

Niu states, “We're working with colleagues in China and Japan on follow-up studies to determine whether this physical response can be measured in other seismically active regions. Provided the effect is pervasive, we still need to learn more about the timing of the signals if we are to reliably use them to warn of impending quakes." [Science Daily]

With hundreds, or even thousands, of people killed and injured in a major earthquake, this new technology could someday save millions of lives as it routinely predicts the beginning of earthquakes so people can seek safety and emergency squads can be dispersed to handle upcoming dangerous situations. Meteorologists on TV weather programs may, one day, include such forecasts in their weather predictions.